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Öğe An acoustic signal based language independent lip synchronization method and its implementation via extended LPC(IEEE, 2020) Cankurtaran, Halil Said; Boyacı, Ali; Yarkan, SerhanProcessing human speech with the use of digital technologies leads to several important fields of research. Speech-to-text and lip-syncing are among the instances of relevant prominent research areas. In this regard, audio-visualization of acoustic signals, providing visual aid in real-time for disabled people, and realization of text-free animation applications are just to name a few. Therefore, in this study, a language-independent lip-sync method that is based on extended linear predictive coding is proposed. The proposed method operates on baseband electrical signal that is acquired by a standard single-channel off-the-shelf microphone and exploits the statistical characteristics of acoustic signals produced by human speech. In addition, the proposed method is implemented on an embedded system, tested, and its performance is evaluated. Results are given along with discussions and future directions.Öğe Adaptive Envelope Detector-Based Phase Fault Detection Method for Power System Grid Distortions(Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Ekti, Ali Riza; Wilson, Aaron; Piersall, Elizabeth; Snyder, Isabelle; Yarkan, Serhan; Stenvig, Nils MIn this study, a phase fault detection algorithm is developed by employing the envelope detector method. The proposed method diagnoses faults among phases and defines fault areas in the incoming signal. The designed algorithm consists of three steps: analytical signal conversion, complex magnitude, and fault detection. Initially, an analytical signal is obtained from the incoming power signal to determine the instantaneous amplitude and phase of the signal. A complex magnitude operation is applied to analytical signals to display changes in amplitude. On the basis of the threshold values specified by the user, the last step identifies the distortion signal in terms of the type of error and size. The proposed method is tested with realistically simulated substation power signal data and real power system data from the Grid Event Signature Library. The obtained results revealed that the proposed method detects distortions accurately.Öğe An adaptive transceiver design for visible light communication(İstanbul Ticaret Üniversitesi, 2019) Yarkan, Serhan; Albayati, SayfWireless Visible light communication has been attracting many researchers attention recently the reasons are that visible light communication have some advantages which does not exist in radio frequency communications. Many researches done in visible light communication fields the most of these researches focused on how to achieve higher communication data rates and much less focused on the designing steps of the visible light communication transceiver to be utilized for indoor applications within short ranges. In this thesis designing and implementing of a visible light communication transceiver is successfully accomplished. The designed system composed of two main sections the transmitter section and the receiver section. The system uses two ATmega328P chip microcontrollers. Light emitting diodes used at the transmitter section as the transmitting module. The light emitting diode illumination light wave acts as the carrier of the transmitted signals. At the receiver section a photo detector and an LCD display are used to realize the signal reception. The final tests of the system showed that the design realizes indoor visible light short distance data transmission and verifies a reliable transceiver for visible light communication.Öğe Analysis and Compensation of Tx and Rx IQ Imbalances in Uplink IM-OFDMA Systems(Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.Index modulation-based orthogonal division multiple access (IM-OFDMA) has recently been proposed as a potential technique for future wireless communication systems due to its su perior spectral efficiency and error performance over conventional multiple access schemes. However, its performance is still under investigation by researchers in light of a variety of scenarios and assumptions. Following this direction, in this Article, the individual and joint effects of the transmitter (Tx) and receiver (Rx) in-phase and quadrature imbalances (IQI) on the bit-error-rate (BER) per formance of the uplink IM-OFDMA scheme are investigated by considering whether each user’s RF front-end is identical or not. Moreover, to reduce the detrimental effect of IQI, a preamble-based estimation and compensation method is proposed for IM-OFDMA. Closed-form expressions for the average BER of IM-OFDMA are obtained by considering the physical effect of the Tx and Rx IQI. Also, using Monte Carlo simulations, the derived expressions are verified under different system configurations. Analytical and sim ulation results reveal that Tx and Rx IQI cause an error floor in the BER performance of IM-OFDMA schemes. However, the proposed estimation and compensation method not only reduces the impact of IQI but also leads to a better BER performance compared to the case of no IQI, which mainly refers to the frequency diversity caused by the IQI.Öğe CNN-Based Signal Detector for IM-OFDMA(Institute of Electrical and Electronics Engineers Inc., 2022) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.The recently proposed index modulation-based up-link orthogonal frequency division multiple access (IM-OFDMA) scheme has outperformed the conventional schemes in terms of spectral efficiency and error performance. However, the induced computational complexity at the receiver forms a bottleneck in real-time implementation due to the joint detection of all users. In this paper, based on deep learning principles, a convolutional neural network (CNN)-based signal detector is proposed for data detection in IM-OFDMA systems instead of the optimum Maximum Likelihood (ML) detector. A CNN-based detector is constructed with the created dataset of the IM-OFDMA transmission by offline training. Then, the convolutional neural network (CNN)-based detector is directly applied to the IM-OFMDA communication scheme to detect the transmitted signal by treating the received signal and channel state information (CSI) as inputs. The proposed CNN-based detector is able to reduce the order of the computational complexity from O(n2n) to O(n2) as compared to the ML detector with a slight impact on the error performance.Öğe A comparison on energy detector and CNN-based detector(IEEE, 2020) Tokgöz, Gamze Kirman; Tekbıyık, Kürşat; Kurt, Güneş Karabulut; Yarkan, SerhanIn today's wireless communication technology, users are classified and assigned to the spectrum by licensing method. There are two types of users in cognitive radio technology, licensed and unlicensed. While primary users use a fixed frequency band, secondary users can detect frequency gaps by different methods, enabling communication when primary users are not using it. With cognitive radio technology, it is aimed to meet the increasing user demands and to make communication faster as a result of using spectrum gaps more efficiently. In this study, energy detector and convolutional neural network (CNN) are compared and investigated which can be more efficient in spectrum sensing.Öğe Detection of Grid-Signal Distortions Using the Spectral Correlation Function(Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Ekti, Ali Riza; Wilson, Aaron; Holliman, John; Piersall, Elizabeth; Yarkan, Serhan; Stenvig, NilsThis study proposes a novel method for signal detection and feature extraction based on the spectral correlation function, enabling improved characterization of grid-signal dis tortions. Our approach differs from existing treatments of signal distortion in its analysis of the varied spectral content of signals observed in real-world scenarios. The method we propose has state-of-the-art discriminative power that provides meaningful and understandable characterizations of various grid events and anomalies. To validate the approach, we use real world data from the Grid Event Signature Library, which is maintained jointly by Oak Ridge National Laboratory and Lawrence Livermore National Laboratory.Öğe Detection, identification, and direction of arrival estimation of drone FHSS signals with uniform linear antenna array(IEEE, 2021) Kaplan, Batuhan; Kahraman, İbrahim; Ekti, Ali Rıza; Yarkan, Serhan; Görçin, Ali; Özdemir, Mehmet Kemal; Çırpan, Hakan AliSafety, security, and privacy are three critical concerns affiliated with the use of drones in everyday life. Considering their ever-shrinking sizes and capabilities, being aware of drone activities in the vicinity becomes an important surveillance item. Therefore, keeping track of drones and preferably their controllers should be included into the already-existing security measures. In this study, a frequency hopping spread spectrum (FHSS) type drone controller signal detection and emitter direction finding framework is proposed to achieve aforementioned goals. Since drone communications signals generally coexist with other FHSS signals in 2.4 GHz industrial, scientific, and medical (ISM) band, first, a method based on cyclostationarity analysis is proposed to distinguish the drone radio controller signals from other signals utilizing 2.4 GHz ISM band. Then, a variant of short-term Fourier transform is introduced to extract the parameters of detected drone remote controller signals. The correct hopping signals are then aggregated based on the clustered parameters to obtain their combined baseband equivalent signal. Furthermore, the resampling process is applied to reduce the unrelated samples in the spectrum and represent the spectrum with the reconstructed signal, which has a much lower bandwidth than the spread bandwidth. Finally, two different multiple signal classification algorithms are utilized to estimate the direction of the drone controller relative to the receiving system. In order to validate the overall performance of the proposed method, the introduced framework is implemented on hardware platforms and tested under real-world conditions. A uniform linear antenna array is utilized to capture over-the-air signals in hilly terrain suburban environments by considering both line–of-sight and non–line–of-sight cases. Direction estimation performance is presented in a comparative manner and relevant discussions are provided.Öğe Ev2c: extended vehicle–to–cloud model and conceptual implementation for big data(IEEE, 2015) Özpınar, Alper; Boyacı, Ali; Yarkan, Serhan; Öztürk, ErdinçGreen transportation is an integral part of green environment concept. Next generation transportation systems are desired to achieve high performances with reduced fuel consumption and carbon emission. In this regard, vehicle maintenance status along with some other critical diagnostic data should steadily be checked and tracked. It is known that vehicles that are poorly maintained or not maintained in a timely manner lead to both emissions exceeding the standards and low performance. Vehicle telematics along with some other conveniences such as infotainment systems, location–based services and applications are expected to improve safety, availability, and reliability of next generation transportation systems. From this perspective, intelligent transport systems (ITS) seems to be a promising solution candidate which encompasses all of the aforementioned topics as well as vehicle–to–vehicle (V2V), vehicle–to–infrastructure (V2I), and vehicle–to–cloud (V2C) opportunities. Therefore, in this study, a conceptual model that links vehicle telematics to the cloud along with V2V communications facility is proposed and a prototype based on IEEE 802:11x protocol suite is implemented. Mobile data collection and measurements are obtained. Results are presented along with relevant discussions as well as the end point storage and usage of the data are introduced. In the proposed model, the mobile data are transferred to cloud computing platform to create the big data for further research opportunities for car manufacturers, policy makers, and researchers with the concern of ethics and security issues.Öğe An Experimental Setup for Mechanical Vibration Analysis Using VLC(Institute of Electrical and Electronics Engineers Inc., 2024) Yılmaz, Ahmet Mücahit; Boyacı, Ali; Ekti, Ali Rıza; Yarkan, SerhanThis study explores the potential applications across various domains, including earthquake detection and warning systems, where the system's sensitivity to ground vibrations can contribute to early seismic event detection. Additionally, the study paves the way of developing applications of VLC/T in mechanical vibration and stability analysis of engines and platforms, offering insights into structural integrity and performance optimization. These multifaceted applications underscore the adaptability and potential of VLC/T systems in diverse fields, heralding advancements in sensing, communication, and security technologies. To achieve this, in this study, Peak to Average Power Ratio (PAPR) is proposed to represent the impact of mechanical shocks and vibrations generated by several weights dropped onto the platform with which the receiver is fixed. Even though non-contact measurement methodology is preferred for various reasons, the proposed measurement campaign obtains the data in contact form; however, the system and signal model proposed in this study could easily be extended into non-contact form. Considering the fact that the proposed measurement campaign employs off-the-shelf products, it is cost-effective and very scalable. © 2024 IEEE.Öğe Fractional-Rate Radiometer for Spectrum Sensing Based on I/Q Branch Separation(IEEE, 2015) Boyaci, Ali; Yarkan, Serhan; Sonmez, A. CoskunRadiometer has a peculiar place among spectrum sensing techniques available in the literature, because it has a simplistic design and is known to be the optimal detector in the absence of a priori knowledge about the signal to be detected. In this study, it is shown that simplicity in the traditional radiometer design could further be improved while its performance is maintained. The proposed method exploits the inherent orthogonality between the I/Q branches and reduces the total number of addition and multiplication operations at baseband. Results are validated by the experimental data collected under different digital modulation scenarios. Relevant discussions and future directions are outlined as well.Öğe A fractionally asymmetric sub–nyquist baseband receiver design and implementation for phase modulated signals(Institute of Electrical and Electronics Engineers Inc., 2022) Gurkas-Aydin, Zeynep; Yarkan, SerhanSub–Nyquist sampling is a technique which has various applications in signal processing and communication technologies. Memory relaxation, peripherals operating at relatively lower speeds, and consequently low–power consumption designs are prominent motivations in sub–Nyquist receiver studies. Although these motivations seem to be attractive, instability and information loss are major drawbacks of sub–Nyquist approaches in comparison with Nyquist–Shannon sampling applications. Nevertheless, sub-Nyquist receivers could still provide several ways of recovering information to some extent in case they are fortified with appropriate interpolation mechanisms. Hence, this study proposes a fractionally asymmetric sub–Nyquist baseband receiver design for phase modulation (PM) signal reception. The proposed method takes advantage of statistical behaviors of the received signal passing through physical propagation medium and adopts an autoregressive process to recover the phase information required. The proposed design is implemented on a software-defined radio (SDR) platform operating in near real–time and tested in a real–world communication environment. Results and discussions are provided along with the future directions.Öğe GERÇEK-ZAMANLI, KISA MESAFELİ VE YAZILIM TABANLI BİR SAYISAL KABLOSUZ HABERLEŞME ALICI-VERİCİ TASARIMININ GERÇEKLEMESİ(2015) Akın, Merve; Çakır, Meryem; Yıldız, Dilara; Özgen, Haluk; Yarkan, SerhanKablosuz haberleşme sistemlerinde alıcı-verici tasarımlarının fiziksel katmanı, sistemin bütününün inşasında oldukça önemli bir yer tutmaktadır. Ancak her yeni çıkan kablosuz haberleşme teknolojisi, hem alıcı-verici tasarımlarının hem de bu tasarıma ait donanımın yenilenmesini zorunlu kılmaktadır. Bunun yanında, sayıları hızla artan kablosuz haberleşme sistemleri, sınırlı ve oldukça değerli bir kaynak sayılan radyo spektrumunun da verimli kullanılması konusunu gündeme getirmektedir. Yakın zamanda ortaya atılan akıllı radyo kavramı; yazılım-tabanlı platform üzerinde çalışmasının bir sonucu olarak; esnek tasarım, değişen koşullara hızlı ve etkin bir biçimde uyum sağlama, spektrumun kullanım durumundan haberdar olma ve öğrenme gibi özellikleri ile sözü edilen konulara yeni bir bakış açısı getirmektedir. Bu çalışmada, akıllı radyo hedefine ulaşma amacı doğrultusunda temel bantta çalışan ve bütün değişkenleri geliştirici tarafından ayarlanıp, denetlenip, güncellenebilen yazılım-tabanlı bir kablosuz akustik alıcı-verici tasarımı ortaya konmuştur. Tasarım ile ilgili kuramsal ve simülasyon tabanlı çözümlemeler verilmiştir. Tasarımın gerçek-zamanlı olarak çalışan bir öntürü gerçeklenmiştir. Aynı öntür yazılım-tabanlı platformlar için de birçok karşılaştırmanın yapılabileceği bir sınama ortamı olarak kullanılabilmektedir. Başarım sonuçları, ilgili tartışmalar ve geleceğe yönelik çalışmalarla birlikte irdelenmiştir.Öğe High-Resolution Multi-band Spectrum Occupancy Measurements and Evaluations at 900MHz Downlink Band for Istanbul Metropolitan(IEEE, 2015) Aki, Fatma Nur; Boyaci, Ali; Yarkan, SerhanRadio frequency spectrum is one of the most important resources for both contemporary and next generation wireless communications (NGWC) systems. Therefore, utilization of the radio frequency spectrum is a critical task. Reliable occupancy statistics are key to such utilization. Considering the fact that Turkey will migrate to digital terrestrial TV broadcast in the near future, a specific portion of the radio frequency spectrum will be available. Hence, occupancy statistics and relevant analyses are mandatory for both contemporary and NGWC systems. Results of high-resolution multi-band spectrum occupancy measurements at 900MHz downlink band for Istanbul metropolitan are presented. Two of the prominent evaluation methods and corresponding occupancy statistics are given in a comparative manner. It is observed that parameters of the evaluation methods affect the occupancy statistics drastically.Öğe Kızılötesi damar görüntüsü işleme ve damar tespiti(İstanbul Ticaret Üniversitesi, 2021) Çankaya, Göksel; Boyacı, Ali; Yarkan, SerhanYüksek güvenlikli kişisel tanımlama giderek daha da önemli hale gelmektedir. Kimlik doğrulama için biyometrik imzalar kullanılmaktadır. Damar desenli kişisel doğrulama insan biyometrik imzalarından biridir. Damar desenli kişisel doğrulama güvenlik uygulamalarının yanında sağlık alanında da çok kullanılmaktadır. Obez kişilerin, koyu tenli kişilerin veya yanık vakaları gibi damarın bulunmasını zorlaştıran durumlarda tedavide veya muayenede güçlükler yaşanmaktadır. Kimlik doğrulamanın güvenilirliğini arttırmak ve sağlık alanındaki dezavantajları gidermek için birçok damar görüntüleme tekniği geliştirilmiştir. Bu çalışmada bu teknikler test edilmektedir. Gelecek çalışmalarda görüntü işleme yapılan görüntülerin ham görüntünün alındığı bölgeye geri yansıtılması hedeflenmektedir.Öğe Location estimation on mobile networks(İstanbul Ticaret Üniversitesi, 2021) Kılıç, Ahmed Hakan; Boyacı, Ali; Yarkan, SerhanThis paper reports the location estimation on Mobile networks using Base Station (BTS) data. Processed data have been collected from the field as TA (Timing Advance), RSRP (Reference Signal Received Power), and RSRQ (Reference Signal Received Quality) measurements. We also gathered the corresponding Global Positioning System (GPS) to the measurements. Location estimation results compared to the actual location. We gathered the accurate sites of the users to increase the service quality of the BTS. This article was produced from the thesis titled “Location Estimation on Mobile Networks.”Öğe Loop-based Markov Chain for next cell prediction(İstanbul Ticaret Üniversitesi, 2023) Yalın, Bahadır; Yarkan, SerhanIn this study, next possible cell for a User Equipment is predicted for Network Data Analytics Function (NWDAF) by using Markov Chain with novel loop-based approach. At the beginning, it is assumed that the prediction made for next state of a User Equipment will be more meaningful with our novel approach. As a result of the study, the transition states between the most visited cell after the last cell where a User Equipment is located were extracted and it was observed that the reliability of the prediction made is improved, when a semantic was established between two cells with the loop-based Markov Chain approach.Öğe A low-cost, high-precision signal generation algorithm and prototype implementation for software-defined radios(Institute of Electrical and Electronics Engineers Inc., 2017) Alaca, Ozgur; Boyaci, Ali; Yarkan, SerhanNext generation wireless communications systems are built on highly-adaptive components in order to meet the ever-increasing requirements and to keep up with the dynamically changing environmental conditions. Software-defined radio (SDR) is considered among vital components of next generation wireless communications due to its capabilities such as spectrum monitoring and sensing along with application-specific waveform generation as well as fast switching between several standards. Therefore, it is expected from SDR that it fulfills fundamental communications operations and functionalities of high-precision with the lowest computational complexity. In this study, a low-computational complexity and high-precision signal generation algorithm operating on digital signal processor (DSP) is proposed for SDR and implemented. Its performance results are compared with those of several algorithms. Results are discussed along with future directions. © 2016 The Chamber of Turkish Electrical Engineers.Öğe A Low-cost, High-precision Signal Generation Algorithm and Prototype Implementation for Software-Defined Radios(IEEE, 2016) Alaca, Ozgur; Boyaci, Ali; Yarkan, SerhanNext generation wireless communications systems are built on highly-adaptive components in order to meet the ever-increasing requirements and to keep up with the dynamically changing environmental conditions. Software-defined radio (SDR) is considered among vital components of next generation wireless communications due to its capabilities such as spectrum monitoring and sensing along with application-specific waveform generation as well as fast switching between several standards. Therefore, it is expected from SDR that it fulfills fundamental communications operations and functionalities of high-precision with the lowest computational complexity. In this study, a low-computational complexity and high-precision signal generation algorithm operating on digital signal processor (DSP) is proposed for SDR and implemented. Its performance results are compared with those of several algorithms. Results are discussed along with future directions.Öğe A low-cost, real-time, and short-range software-defined digital wireless communications transceiver design and implementation at baseband(Gazi Universitesi Muhendislik-Mimarlik, 2015) Akin, Merve; Çakir, Meryem; Yildiz, Dilara; Özgen, Haluk; Yarkan, SerhanPhysical layer transceiver design lies in the heart of all wireless communications systems. However, each and every emerging wireless communications technology forces the already-existing transceiver designs and their corresponding hardware to change. In addition, due to the dramatic increase in number of emerging wireless technologies, there are serious concerns regarding the utilization of valuable radio spectrum. Recently, cognitive radio concept is proposed in order to provide a new perspective for the aforementioned concerns. Operating on a software-defined platform, cognitive radio introduces flexibility in design of utmost level; adapts itself to the dynamic radio environment; senses the radio spectrum steadily to be aware of it; and learns about its past experiences in order to plan and take action in the future in a beter way. Therefore, in this study, a software-defined wireless acoustic baseband transceiver design whose each and every parameter could be modified, updated, and changed with utmost flexibility is established toward realization of cognitive radio. Mathematical analysis and a simulation environment of the design are provided too. A real-time implementation of the transceiver is realized as well in order to both demonstrate an operating prototype and set up a testbed for software-defined platforms. Results for theoretical, simulation, and real-time performance of the transceiver are given along with relevant discussions and future directions.
